Fatigue machine for testing materials submitted to alternated or repeated tensile stresses



R. LHERMITE Filed NOV. 16, 1945 FATIGUE MACHINE FOR TESTING MATERIALSSUBMITTED TO ALTERNATED OR REFEATED TENSILE STRESSES April 19 19'wzcccccccczccsczzcc I A mns/vro/e Roamr [HEM/0'5 uuuuuuuuuu PatentedApr. 19, 1949 UNITED STATES PATENT OFFICE FATIGUE MACHINE FOR TESTINGMATE- RIALS SUBMITTED TO ALTERNATED OR REPEATED TENSILE STRESSESApplication November 16, 1945. Serial No. 629,022 In France November 20,1944 6 Claims.

The main feature of this fatigue machine for testing materials is thatall the adjustments, notably the measurement and adjustment of theamplitude of the vibrations imposed upon the test-piece, can beperformed while the machine is in operation.

Fig. 1 shows a machine according to the invention.

Fig. 2 shows an arrangement for the measurement of the stress.

Fig. 3 shows an automatic command to stop the machine.

A vibratory motion is applied to the head l6 of the test-piece I, andthe stress on the latter is measured with the aid of a dynamometricsprin 2 arranged in series therewith (Fig. 1).

The test-piece head It is acted on by one end 2|] of a lever with a1:3.5 ratio whose three pivots l1, l8, I9 are mounted in needle bearingswhile the other lever end 2| is connected with a link 4 whose free endcan be moved along a curved slideway 5 provided in a pivoted arm 25 theradius of which slideway is equal to the length of the link 4; theposition of said link is defined by a pair of rods 6 whose ends 22, 23are connected on one hand with link 4 and on the other hand with a nut 1that can be displaced in parallel motion by the actuation of thewormspindle 8.

The pivoted arm 25 is fulcrumed to the stationary pin 9 mounted inneedle bearings; the movable end 24 is acted on by a rod i actuated by acrankshaft ll carried in a pair of ball bearing pedestals. Keyed on saidcrankshaft is a flywheel 26 intended to cushion the cyclicirregularities of the moving system. Said flywheel 35 also serves as apulley and is driven by the motor through a suitable reduction gear.

Through the provision of the pivoted arm provided with a slideway itbecomes possible, simply by displacing point A along the slideway bymeans of the worm-spindle 8, to vary the amplitude of the variations inthe load upon the test-piece; maximum amplitude is obtained at point B,and all the positions between the two said points can be obtainedeasily.

A measurement of the stress is obtained by ascertaining the deformationsof spring 2 by means of a device composed of a pair of comparators andillustrated in Fig. 2.

A small carriage 3| controlled by a worm spindle 32 carries the onecomparator 33; the displacements of said carriage 3i and consequently ofthe point of the comparator 33 are measured with the aid of the othercomparator 34.

In the operation of the machine, as the carriage 3| is displaced and thepoint of the comparator 33 comes just into engagement with the spring,the pointer of comparator 33 jolts violently, which allows accurately toascertain the extreme position of the spring.

A device is provided for automatically stopping the machine when thetest-piece breaks.

As shown in Fig. 3 such device comprises a contact 4| which closes whenthe spring is back to its position of balance; said contact controls bythe electric circuit 42 a small relay not shown which in turn controls acircuit-breaker not shown.- Said device serves also to protect the r I lmotor against overlntensities and overloads.

Moreover, the machine can operate only provided a test-piece is mountedtherein.

What I claim as my invention and desire to 0 secure by Letters Patentis:

a pivoted arm provided with a slideway oscillated about another fixedaxis, means to impart to said pivoted arm an angular motion of constantamplitude, an articulation adjustable in said slideway of said pivotedarm, a link connecting said lever to said articulation and means toadjust the point of articulation of said link in said slideway of saidpivoted arm as desired for the purpose of adjusting the amplitude ofoscillation of said lever.

, 2. A machine for testing materials submitted to alternated or repeatedtensile stresses comprising a spring bar one end of which is set in afixed support, a lever oscillatable about a fixed axis, means betweenwhich a test-piece can be tensioned one of which is pivoted on the otherend of the spring bar and the other is pivoted on one end of saidoscillatable lever, a pivoted arm provided with a curved slidewaymovable about a fixed axis, means whereby an oscillatory movement ofconstant amplitude can be imparted to said pivoted arm, an articulationadjustable in said slideway of said pivoted arm, a link connecting theother end of said lever to said pivoted 5 arm and means whereby theposition of the point of articulation of the link in the slideway of thepivoted arm can be adjusted along the latter.

3. A machine as claimed in claim 1 in which the slideway of the pivotedarm is curved on a radius equal to the length of the link connecting 3the articulation adjustable in the slideway of the pivoted arm with thelever.

4. A machine according to claim 3 in which the means to adjust theposition of the point of articulation of the link in the slideway of thepivoted arm comprise a rotatable worm spindle, a nut cooperating withsaid worm spindle anda rod one end of which is pivoted on the nut andthe other end of which is pivoted on the point of articulation of thelinkin the slideway of the pivoted arm.

5. A machine as claimed in claim 1 in which the means by which anoscillatory movement is imparted to the pivoted arm comprise a motor, acrank shaft actuated by said motor and a rod one end of which ispivoted" on said crankshaft and the other end of which is pivoted on thefree end of the pivoted arm.

6. A machine as claimed in claim 1 in which the means by which anoscillatory movement is imparted to the pivoted arm comprise a motor,

REFERENCES CITED The following references are of record in the file ofthis patent! UNITED STATES PATENTS Number Name Date 1,409,842 FosterMar. 14, 1922 1,637,011 Schopper July 26, 1927 1,921,793 Thelander Aug.8, 1933 2,154,277 Moore Apr. 11, 1939 2,215,958 Fullerton Sept. 24, 1940

